A noninvasive method has been developed for sequentially measuring left ventricular performance and myocardial segmental function following cardiac surgery in man. Radiopaque tantalum markers are implanted in the mid-wall of the left ventricular myocardium at the time of surgery and subsequently visualized in radiograms which are stored on a video disc recorder. A light-pen/computer system is used to obtain measurements of: end diastolic volume, end systolic volume, stroke volume, ejection fraction, heart rate, cardiac output, mean segmental shortening, systolic duration, mean circumferential shortening velocity, asynergy, a ventricular velocity-synergy index, and instantaneous segmental dynamics. The method provides, in essence, a "noninvasive cineventriculogram" which can be obtained and analyzed by computer as often as desired after cardiac surgery without risk or discomfort to the patient. Five projects are proposed utilizing intramyocardial markers in man: 1) An evaluation of postoperative function and wall motion in patients having aortocoronary bypass graft surgery, 2) A study of the effects of rejection on left ventricular dynamics after cardiac transplantation, 3) An assessment of ventricular function and ventricular wall motion changes occurring as a result of pharmacologic and physiologic interventions in the innervated and denervated heart, 4) An assessment of the effects of cardiac rehabilitation, including a regular exercise program, on postoperative ventricular function, and 5) An assessment of postoperative changes in cardiac function following valve replacement. BIBLIOGRAPHIC REFERENCES: Ingels, N.B., Jr., Daughters, G.T., II, Stinson E.B., and Alderman, E.L. Measurement of midwall myocardial dynamics in intact man by radiography of surgically implanted markers. Circulation 52:859, 1975. Ingels, N.B., Jr., Daughters, G.T., II, Alderman, E.L., and Stinson, E.B. Measurement of instantaneous left ventricular dynamics in intact man by radiography of surgically implanted markers. Proc. 28th A.C.E.M.B. Sept. 1975, New Orleans.